A resin molding die includes a core mold generally having a shape corresponding to an inner surface of a resin-molded product and a cavity mold provided so as to be engageable with the core mold and generally having a shape corresponding to an outer surface of the resin-molded product.
In such a resin molding die, a space (cavity), which is formed under a state in which the core mold and the cavity mold are engaged with each other, has a shape corresponding to the resin-molded product, and a molten resin is injected into the cavity to be cured. In this manner, the resin-molded product is manufactured (Patent Literatures 1 and 2).
In this case, after the resin is cured, it is necessary to separate the core mold and the cavity mold to take out the resin-molded product from the resin molding die. However, when an uneven shape or a through hole that intersects with (is orthogonal to) the separating direction (mold removal direction) is formed on or in the resin-molded product, the resin-molded product cannot be taken out from the resin molding die as it is.
Such a shape is referred to as “undercut”.
In a die for molding the resin-molded product comprising an undercut, the following method is known. A portion at which the undercut is formed is provided as an independent component, and the component is removed while being moved in a direction different from the mold removal direction, to thereby take out the resin-molded product from the resin molding die (Patent Literature 3).
In this case, when the undercut is a through hole that is formed perpendicularly to the mold removal direction for the resin-molded product, the undercut may need to be provided on the core mold.
Specifically, a pin-like protrusion corresponding to the through hole is provided on the core mold, and a peripheral part of the protrusion is provided as a slide core, which is movable in a direction that is inclined with respect to the mold removal direction.
On the other hand, when three-dimensional decoration called “embossed surface” is provided on a surface of the resin-molded product, a process of engraving a pattern called “embossing process” needs to be performed on an inner wall of the cavity mold (Patent Literature 4).